BOGOTA - At least 16 police were killed Tuesday in Colombia when a helicopter taking part in an anti-drug trafficking operation crashed in a remote jungle-covered region, officials said.

A total of 18 officers were on board the Blackhawk helicopter, which was involved in an operation against the powerful Clan Usuga drug gang in northwestern Colombia's Antioquia department, said Defense Minister Luis Carlos Villegas.

The other two were taken to a nearby hospital with second- and third-degree burns, he told a press conference.

"Unfortunately, the prognosis is not good," he said, adding there was no indication of foul play. Villegas said "thick jungle" and "rough terrain," as well as bad weather, had delayed the operation, which had been due to begin at 5:30 am.

"For the moment, the most likely theory is that the helicopter crashed into the hillside at a speed of 120 knots, which is 180 kilometers per hour, possibly because of low clouds. The helicopter was found absolutely destroyed," he said.

It is the second deadly crash to hit the Colombian security forces in recent days. On Friday, 11 soldiers were killed when the air force plane transporting them went down in the Las Palomas region. The pilot in that crash had reported engine trouble.

Clan Usuga is the main drug gang in Colombia, the world's leading producer of coca, the raw ingredient for cocaine. President Juan Manuel Santos's government has intensified its offensive against the gang in recent months.

A UN report recently found coca cultivation in Colombia exploded 44 percent last year, yielding potential cocaine production of 442 tonnes - a 52 percent increase from 2013.