Ferrisburgh, Vt. — Investigators plan to release a preliminary report within 30 days on a fatal plane crash over the weekend that killed four people from Connecticut, including a Middletown High School sophomore, her mother and a teacher at the school.

But an official with the National Transportation Safety Board said Tuesday that a final report outlining the probable cause of the crash could take up to two years to be released.

The timeline for the preliminary information and final report, which was outlined during a news media briefing Tuesday afternoon, is in line with other fatal crashes involving general aviation aircraft.

Authorities said Paul Pelletier, 55, of Columbia, Frank Rodriguez, 88, of Lebanon, and Susan Van Ness, 51, and Delilah Van Ness, 15, both of Middletown, all were killed in the crash Sunday.

Pelletier was a teacher at Middletown High School. Delilah Van Ness was a sophomore at the school and daughter of Susan Van Ness, school officials said.

The group had flown from Windham Airport in Connecticut to Basin Harbor Airport in Ferrisburgh, Vt., where they had a "lunch reservation," said Kurt Gibson, an aviation accident investigator with the NTSB. They were heading back around 12:25 p.m. when the single-engine Piper Arrow the group was flying in crashed into the ground just south of Basin Harbor Airport, Gibson said.

The grass airstrip sits on a broad hook of land that juts into Lake Champlain. The 3,000-foot airstrip is open to the public and has been in operation since the 1950s, but only is open from early spring to late fall, according to information available to pilots. The runway becomes soft after heavy rains, and the primary surface area of the runway is "deficient" and cluttered with 50-foot trees on either side of the southern half of the runway.

About three-quarters of an inch of rain was recorded in Burlington about an hour north of the airport between Saturday and Sunday, according to the National Weather Service.

"Gusty winds will be the biggest concern on Sunday as wind gusts upwards of 30 knots" — about 35 mph — "from the west will impact all terminals leading to cross winds at many airports," the weather service warned in its aviation forecast discussion.

Gibson, the NTSB investigator, said Tuesday that the wreckage of the plane was to be removed that day and taken to a salvage facility to be examined.

"This is just the initial process of the NTSB, we're just here to gather perishable information at the accident scene and to document the accident scene and also to document anything that might get damaged during the recovery process," Gibson said.

He said he would be examining the aircraft wreckage for signs of any "mechanical malfunctions or anomalies," that could have contributed to the crash. Investigators also will be looking at the pilot, including his qualifications, and getting a "72-hour history of him," Gibson said, as well the environment — the weather conditions, any involvement with air traffic controllers and the runway itself.

Robert Katz, an aviation expert who has been a pilot for 43 years, said the aircraft might have been overloaded with four passengers, whose weight may have been unevenly distributed.

Federal Aviation Administration records show the plane was made in 1967. It's considered a "high-performance plane," according to Katz.

Gibson said the aircraft is not required to have a "black box" like an airliner. However, "there are newer avionics that can be installed in these aircraft," he said, referring to electronic aviation systems. Those devices "do contain some non-volatile memory that might contain some data," which will be sent to the NTSB's lab in Washington, D.C., Gibson said.