The FBI Monday joined the manhunt for the winery worker who slaughtered seven people, including two young daughters, and eluded an army of lawmen in northern California's pastoral wine country.

Authorities said Ramon Salcido, 28, may have headed toward his native Mexico after the rampage, which started on Friday on a dirt road on the vineyard where he was an employee.FBI Agent Chuck Latting said his agency would obtain a fugitive warrant from a U.S. magistrate in San Francisco as soon as the Sonoma County Sheriff's Department obtained a local warrant. Latting said agents already have started an operation to catch the hot-tempered, hard-drinking Salcido.

"Our agents have become deeply involved," Latting said. "Our scouts are already out there."

The Customs Service in Los Angeles admitted there were miles of "isolated terrain" along the U.S.-Mexican border where Salcido could leave California and it would be difficult to catch him there.

Latting was unsure if Salcido had become a naturalized American since leaving Mexico. If Salcido has American citizenship and is caught across the border by Mexicans, it would not be difficult to extradite him to the United States. But, the agent said, it would be "much touchier" if he were a Mexican citizen.

One of Salcido's victims was his wife, Angelia, 24, whose body was found Friday in their Boyes Hot Springs home near Santa Rosa. Sources said her December 1984 marriage to Salcido helped him get a green card to remain in California. Investigators said it was unknown whether Salcido later became a U.S. citizen.

Salcido, after killing his co-worker and his wife, took his three small children and slashed their throats, deputy sheriffs said, and dumped them into a rural landfill near Petaluma.

Two of the girls were dead when a man found them Saturday while scavanging for auto parts, but 2-year-old Carmina was still alive and was recovering Monday following surgery to repair her wounds.

Carmina was under police guard at Petaluma Valley Hospital and in stable condition.