SAN DIEGO -- On Friday, a border tunnel was found in Otay Mesa. Now it appears agents from the United States and Mexico have found what appears to be a second tunnel that could be a part of an underground network, 10News reported.

"It's a project we've been working on exhaustingly for past three to four months," said Mike Unzueta, who is the head of the Immigration and Customs Enforcement in San Diego.

Unzueta said the newly-created Tunnel Task Force is already discovering fertile ground.

"For us it's very exciting when we actually find one of these things. We've been looking for 10 that never existed," Unzueta said.

It appears that in less than four days, officials from the United States and Mexico have found two tunnels that originate from a metal warehouse in Mexico. On Friday, they found a different tunnel that appears to be connected to the tunnel found on Tuesday morning.

"We have an entrance that's 4 feet by 4 feet. What I've been told is that it leads to a shaft buried very deep into the ground," Unzueta said.

He said once authorities find the connection, it might lead them to exit points in the United States.

"We have caught most of these tunnels while they are still in the construction phase," Unzueta said.

He said that until a link is found, he could not confirm if the tunnels were part of an extended network.