MEXICO CITY (Reuters) - Mexican troops seized a small submarine smuggling drugs in the Pacific Ocean on Wednesday, the military said.

A navy plane spotted the craft about 140 miles south of the tourist resort of Huatulco, setting off a three-hour chase, Rear Adm. Hector Mucharraz told Reuters.

The green-colored submarine, carrying what was believed to be cocaine, was about 32 feet long and appeared to be a makeshift or modified vessel.

“The submarine traveled almost at the surface of the sea and when it came up we took advantage,” said Capt. Benjamin Mar, a navy spokesman. Special forces troops swooped on the submarine from a helicopter and subdued the crew of four, he said.

The Mexican government is increasingly using the military to fight drug smugglers who move South American cocaine through Mexico and into the United States.

President Felipe Calderon has sent thousands of troops to drug trafficking hot spots since he took office in December, 2006.

Smugglers have moved drugs in Mexico through tunnels under the U.S. border and hidden in canned food and dolls, but the navy said this is the first time it had seen them use a submarine.