MEXICO CITY — In a grisly discovery, Mexican marines have found 72 bodies dumped at a ranch in a violence-torn stretch of northern Mexico, the navy announced.

The bodies of 58 men and 14 women found Tuesday were not immediately identified, and it was not clear why or when they were killed.

Tamaulipas, the northern state where the bodies were found, has been rocked by months of violence between feuding drug gangs. But reports in the Mexican media said the victims may have been migrants from Central and South America. Authorities declined Wednesday to comment on the news reports.

The navy said marines found the bodies in a rural zone 80 miles south of the Texas border after a shootout that killed three gunmen and a marine.

Marines backed by navy helicopters were led to the ranch near the town of San Fernando by a man who had been wounded by gunfire. When the troops arrived, they came under fire from gunmen who fled in a caravan, the navy said in a statement issued late Tuesday.

Marines seized 21 assault rifles, shotguns and rifles, thousands of rounds of ammunition, bulletproof vests and four pickups painted to resemble military vehicles. A minor was detained and handed over to the federal attorney general’s office, the navy said.

Navy personnel found the bodies during a subsequent search for the site, which had been mentioned by the wounded man. It was not clear whether the bodies were dumped at the same time.

Tamaulipas state has been shaken for months by violent feuding between the Gulf drug cartel and former allies known as the Zetas. The Zetas, notorious for their brutal methods, have also branched out into migrant smuggling.

Since Mexican President Felipe Calderon announced a crackdown on organized crime in late 2006, the violence nationwide has claimed more than 28,000 lives, mainly due to fighting between rival trafficking groups.

In recent months, several dump sites around the country have yielded scores of dead attributed to the drug war.