A 40-foot boat carrying a tour group of senior citizens capsized on Lake George in upstate New York yesterday afternoon, killing at least 21 of the 49 people on board.

The Warren County sheriff, Lawrence Cleveland, said yesterday that state police were investigating the possibility that the accident was caused by the wake of a larger tour boat.

The Ethan Allen overturned about 700 feet from shore and sank in 70 feet of water, according to sheriff’s reports.

Mr. Cleveland said the accident happened so quickly that passengers could not put on their life jackets.

In New York, adult passengers are not required to wear life jackets.

Patrol boats, divers, and volunteers rushed to the scene to rescue victims, but after two hours the operation changed to recovery from rescue, according to the Associated Press.

The dead were collected and covered in blankets at a nearby campground, witnesses said.

Twenty-seven passengers were taken to a hospital in Glens Falls, where they were treated for a variety of minor injuries.

Several passengers were admitted to the hospital, with most scheduled to be released last night, according to a hospital spokesman, Jason White.

Mr. White said state investigators interviewed passengers at the hospital.

There were conflicting reports early on about the origin of the tourist group. The Associated Press said the group was from Michigan.

The Ethan Allen is operated by Shoreline Cruises. Employees of Shoreline would not comment.

The owner, James Quirk, told the Glens Falls Post-Star: “It is a tragedy and it’s very unfortunate.”

The AP reported that the boat had a maximum capacity of 50 people and was carrying 48 or 49 passengers.

The tragedy occurred on a clear, picturesque early autumn day at the popular tourist destination in the Adirondack Mountains, about 50 miles north of Albany.

Some residents learned of the accident, which occurred about five miles north of town, when local news reports interrupted television coverage of football games. Others heard helicopters in the sky and ambulances careening down the road.

Several witnesses said that one large tour boat, the Mohican, was in the vicinity at the time of the capsizing.

The Mohican, a 117-foot refurbished steamboat originally built in 1907, has a reputation around the lake for its large wake, according to several sources.

The Mohican is operated by the Lake George Steamboat Company, the owner of three large steamboats that carry tourists around the lake.

According to a schedule posted on the company Web site, the Mohican would have been operating a tour through the “narrows” of the lake to Paradise Bay between 2:30 p.m. and 4:45 p.m. yesterday.

According to the AP, the Ethan Allen capsized at about 3 p.m.

The daughter of the owner of the steamboat company, Rebecca Dow, who is also an employee, said she would not confirm that the Mohican caused the capsizing.

“I would be outraged if they are trying to say it is our fault,” Ms. Dow told The New York Sun. “It’s a scapegoat act.”

“The Mohican has run its same course for 20-plus years, and the Ethan Allen has run its same course for [many] years,” Ms. Dow said. “It is too far at the end of the season to point their fingers at the bigger boats.”

Ms. Dow said that boat schedules are posted and known by other captains.

“Maybe their captain wasn’t steering properly,” Ms. Dow said.

An employee of Gilchrist Boat Launching, Maggie Graven, piloted a boat near the scene of the accident soon after it occurred.

“By the time we got down there, they were directing boats away from the scene,” Ms. Graven said. “There were divers everywhere trying to get bodies. They were collecting the bodies on the shore by … the campground.”

Ms. Graven said she suspected that the Mohican had caused the capsizing.

“The Mohican throws out a lot of wake,” she said, adding that when the steamboat cruises past, “It makes our marina look like an ocean.”

Boating accidents on the heavily trafficked 32-mile-long lake are not unusual. Some residents in recent years have sought increased safety measures, including lower speed limits and a ban on personal watercraft.

In 2004, there were 14 boating accidents on Lake George, and the last fatal accident was in 2003, according to the Lake George Park Commission.