The U.S. Coast Guard rescued 16 people from the Pacific Ocean about 140 miles west of Ensenada, Mexico, early Friday after a boat sank, NBC 7 San Diego, The Associated Press and the Los Angeles Times reported. The Coast Guard got a mayday call from the sinking vessel at about 1 a.m., NBC 7 and the Times reported.

A survivor said as many as 27 people had been on board, the AP and the Times reported. Another 11 people are believed to be missing, the AP reported. "They've rescued 16 so far, and one of the rescued survivors reported that there was 27 people on board," Coast Guard Petty Officer Chris Sappey said, according to the Times.

A rescue helicopter reached the site about two hours after the mayday call, the AP reported. "People were holding onto each other, to debris, just treading and trying to stay above water before being rescued," Coast Guard Lt. Santiago Tamburini said, according to the AP. "All we found was debris, and certain floating seats that are starting to give us a better idea of what vessel it may have been," Tamburini said, according to NBC 7.

The survivors were flown to San Diego and taken to hospitals, NBC 7 and the AP reported. San Diego Fire-Rescue Assistant Fire Chief Brian Raines said two people were in critical condition, NBC 7 and the Times reported. Scripps Mercy Hospital was treating one person for a suspected shark bite, NBC 7 and the AP reported.

The Mexican Consulate in San Diego said the 16 survivors are Mexican nationals, NBC 7 reported. The Times, citing the Coast Guard, reported that two had been confirmed as Mexican nationals. Where the boat came from and what it was doing were not clear, the AP reported. "The vessel was reportedly traveling along a route commonly associated with maritime smuggling; however, the circumstances surrounding the incident remain under investigation," the Coast Guard said in a statement, according to NBC 7. "Boats in that area can be for fishing, leisure, personal recreation," Tamburini said, according to the AP.

The Coast Guard and the Mexican Navy were still searching the area, the AP reported.

What we know: Sixteen people were rescued, and a survivor said as many as 27 were on board.
What we don't: What happened to the others, and where the boat was going.