This was one of the more sophisticated tunnels that we've seen

DEA spokesman Don Thornhill

The tunnel connected a private house in the mountains east of San Diego to the Mexican border town of Tecate, said a spokesman for the US Drug Enforcement Administration (DEA).

US officials said that although tunnels had been found between the two countries before, this one was unusually elaborate, equipped with rails, electric lighting, and a ventilation system.

The discovery comes five days before the US director for homeland security, Tom Ridge, arrives in Mexico for border talks.

Drugs seizure

The tunnel appeared to have been in operation for two to three years, said DEA spokesman Don Thornhill.

He said it may have also been used to smuggle illegal immigrants.

At least 200 pounds (91 kg) of marijuana were seized at the scene.

One person was reportedly arrested in connection with the haul.

'Sophisticated'

The tunnel measured four feet (1.2 metres) by four feet and was dug about 20 feet (six metres) underground, according to the Associated Press news agency.

"This was one of the more sophisticated tunnels that we've seen," said Mr Thornhill.

A comparable discovery was made in 1990 when a 270-feet (82-metre) tunnel was found between Douglas in Arizona and a private luxury home in Agua Prieta, Mexico.

The Mexican entrance to that tunnel was concealed underneath a games-room floor, which could be lifted using hydraulics.