SAN DIEGO — Two incomplete tunnels were discovered along the U.S.-Mexico border in what authorities described as a failed attempt to sneak people into the U.S. illegally.

Each tunnel was about 3 feet wide, 3 feet high and 5 feet underground, said Frank Marwood, assistant special agent in charge of investigations at U.S. Immigration and Customs Enforcement in San Diego. They were about 44 yards apart, near San Diego’s Otay Mesa border crossing.

The tunnels were less than 10 feet long; one extended 5 feet into the U.S. and the other went 2 feet in the U.S., Marwood said. The entrances in Tijuana, Mexico, were covered with plywood.

The passages, discovered Wednesday in a joint effort by U.S. and Mexican authorities, are among dozens found along the border in recent years, many clustered around San Diego and Nogales, Ariz.

“This is the lowest-grade kind of tunnel that we’ve found,” Marwood said. “They are pretty much holes in the ground.”

U.S. authorities have found 58 secret tunnels along the Mexican and Canadian borders since 1990, the Department of Homeland Security said earlier this month.

Several are unfilled, including a 2,400-foot-long tunnel that connected Tijuana and San Diego. That passage, discovered last year, was lit and ventilated, equipped with a pulley system, and went as deep as 90 feet.

Homeland Security said it has set aside $2.74 million to fill in seven tunnels by mid-May.