A search for a missing scuba diver in the St. Lawrence River near Cornwall, Ont., is now a recovery operation, according to Ontario Provincial Police. 

OPP say a call came in just before 9 a.m. for a diving incident after two male divers entered the water, but only one returned to shore.

It happened at Lock 21 on Macdonnell Island in South Stormont Township.

Multiple agencies were involved in the immediate search effort, including the RCMP, South Stormont and Cornwall Fire Services, U.S. Customs and Border Protection, and a helicopter from CFB Trenton.

People living in the area tell CTV, it's a popular diving spot.

"This area, Lock 21, the west end, you see a lot of divers going in there," said Peter Palmer.

"15 or 20 times I'll be down here, and we'll see divers going in at that site."

OPP say the divers entered the water at Lock 21, a submerged lock system along the St. Lawrence Seaway. The floor of the lock is about 60 feet deep. 

Search efforts continued late into the evening. The OPP boat rescue alongside RCMP boat rescue were seen searching the water, and what appeared to be an OPP helicopter was flying overhead the scene at around 6:30 p.m. Tuesday. 

The OPP Search and Rescue dive team has been called in. They are travelling in from Thunder Bay and are expected to arrive either late Tuesday night, or early Wednesday morning. The OPP Search and Rescue team will assist with the search tomorrow.