Workers on Monday continued to gather human remains and to search for answers at the site of the plane that crashed outside Moscow, killing all 71 people on board. The emergencies ministry said it had found more than 700 body parts. It will take a week to fully scour the 30 hectares of snowy fields and forests over which debris and human remains were scattered, it said. The authorities found the black box voice recorder on Monday morning, hours after discovering the first black box with flight data, raising hopes for more clues about the plane's sudden demise on Sunday. The An-148 aircraft was heading toward Orsk in the Orenburg region when it plummeted 6,000 feet to the ground without issuing a distress call four minutes after takeoff. A CCTV camera close by filmed a fireball near the ground followed by clouds of thick smoke. Russia's investigative committee said on Monday it was examining the “activities of the airline, the technical condition of the airplane, the pilots' level of professional training”. It said that the airliner had not caught fire nor broken up when it started to go down, and the “explosion occurred after the plane fell,” suggesting that suspicions of a terrorist attack were baseless. A 2017 photo of the Saratov Airlines plane that crashed Credit: Marina Lystseva/AFP/Getty Images Saratov Airlines said on Monday it had temporarily stopped operating its An-148 planes, of which it had six, while the investigation continued. The airliner that crashed was built in Voronezh, Russia, in 2010 and had made only 8,348 flights of its expected lifespan of 40,000. Russia was the most dangerous country for flying in 2011, the year when a professional ice hockey team from Yaroslavl died in a plane crash, among other air tragedies. In December 2016, 64 members of the Red Army choir, well-known humanitarian Elizaveta Glinka and 27 others were killed when a defence ministry airliner crashed into the Black Sea on its way to New Year's festivities at Russia's airbase in Syria. A security camera captured the plane crash that killed 71 outside Moscow today. You can see a fiery explosion and a huge cloud of smoke. @tvrainpic.twitter.com/jCTX52NXZv— Alec Luhn (@ASLuhn) February 11, 2018 Most of the crashes have been caused by pilot error, and the rapid growth of Russia's air industry has led to training concerns. “There was a lack of pilots, they have been training them quickly, putting them in the ranks quickly, and in this hectic atmosphere, the quality decreased,” said Roman Gusarov, editor of the industry news site AviaRu.net. In the aftermath of Sunday's catastrophe, answers were few and far between. President Vladimir Putin has ordered a special commission to look into the causes of the crash. Roses and candles were placed at a monument to a famous Soviet pilot in the Orenburg region to commemorate the victims of the crash Credit: Sergei Medvedev/TASS via Getty Images FlightRadar data showed the An-148 lost several hundred feet of altitude, then climbed again before plunging to earth. Captain Valery Gubanov, a former military pilot and war veteran, had more than 5,000 flight hours, while the second pilot had 812 hours of experience. A Saratov Airlines pilot who had flown the Moscow-Orsk route with the captain of Sunday's flight told Radio Free Europe that he believed “this was a terrorist attack” because body parts were dispersed so widely. “That means there was a powerful explosion on board, otherwise they would not have been so scattered,” he said. RBC newspaper quoted sources near the investigation, however, who said the engines were working until the plane hit the earth. A man holds a candle at Orsk airport, the ill-fated plane's intended destination Credit: TASS/Barcroft Images Witnesses near the crash site told media they had heard a loud boom, although this could have been the fuel tanks exploding on the ground. Other newspaper reports pointed to a technical fault in the plane, which had already made three flights on Sunday. Investigators have taken samples of jet fuel at the Penza airport where the plane's tanks had been refilled. Kommersant reported that the pilot had declined a de-icing procedure before takeoff, while Moskovsky Komsomolets said a state transport watchdog inspection of the plane in November found that gear oil had not been replaced and an air-start system filter had not been cleaned as regularly as it should have been. Emergency workers examine debris from the An-148 plane that crashed on Sunday, killing all 71 on board Credit: Vasily Maximov/AFP/Getty Images An-148 engines have failed in past instances. During a 2011 test flight, faulty airspeed indicators reportedly led the crew to increase velocity until the engines caught fire and the An-148 fell apart in mid-air, killing all six on board. Local authorities have said they will pay compensation to the relatives of those lost on the flight. The dead included Swiss citizen Klaeui Ulrich, who the Orsk oil refinery said had been overseeing the installation of equipment at its facilities. A citizen of Azerbaijan was also on the flight. A man comforts a woman at Orsk airport, where loved ones of the victims gathered on Sunday Credit: TASS/Barcroft Images Three children died, including a five-year-old. Orsk residents have been bringing roses and candles to a Vladimir Lenin monument in the centre and to a local school that lost a 17-year-old student. Orenburg and Moscow canceled festivities on Monday marking the start of Maslenitsa, a traditional holiday before Lent during which Russians bake bliny pancakes and take part in outdoor activities like sledging and bonfires.