A police helicopter crashed in the City of God favela in Rio de Janeiro, killing the four police officers onboard during an operation Saturday.

The helicopter was reportedly assisting on an anti-drug mission. Military police spokesman Maj. Ivan Mlaz told news website Globo the helicopter was forced down but did not elaborate what forced the helicopter down. The police said in a statement that they were investigating the cause of the crash.

Amateur video showed the helicopter spun as it fell and crashed in an open area near a major highway.

Violence back up

After the spotlight of the Summer Olympics went out, violence has crept up in Brazil's second-largest city. Though police were able to push drug traffickers and gangs out of favelas for the 2014 World Cup and 2016 Summer Olympics, the state government, which is responsible for security in the region, faces a a budget shortfall of nearly 20 billion reais ($5.91 billion, 5.58 billion euros).

The murder rate in Rio through September rose nearly 18 percent from the same period in 2015. Street crime, including crime on public transportation, jumped 44 percent.

Though crime in Rio is far lower than its peak in the 1980's and 1990's, this is not the first incident of police aircraft getting shot down. Drug traffickers shot down a helicopter in 2009 and killed two crew members as police attempted to quell violence in preparation for the 2014 World Cup.

kbd/kl (AP, AFP, Reuters)