SOUTH LAKE TAHOE, Calif. (AP) — None of the eight people killed when a boat capsized during a sudden and fierce storm last month on Lake Tahoe in California were wearing life vests, federal investigators said in an initial report released Wednesday.

Four members of a family who were celebrating a birthday were among those who died when the 28-foot gold Chris-Craft vessel was inundated and flipped over amid 10-foot waves June 21 on the lake’s western edge.

Weather was mostly calm when the party of 10 left the marina around noon, but within about two hours winds were strong enough to create whitecaps, according to the preliminary report by the National Transportation Safety Board.

By 2:30 p.m., as the boat was returning to shore, it began to hail and the vessel ended up sideways to the growing waves.

“The boat took on water and some of the passengers attempted to bail the water out of the boat,” the report states. “At one point, a particularly large wave overtook the boat.”

Two people were rescued immediately after it flipped over. One of the survivors was found clinging to a life vest and the other was wearing one, according to the report.

Six people were found dead that afternoon and evening and two more bodies were discovered the next day. None of the people found dead had been wearing life vests, the report said. Four life vests and one life preserver ring from the boat were recovered from the accident site.

Hikers on shore called 911 after witnessing the vessel capsize. No distress calls were made from the boat, the report said.

Toxicology tests for alcohol and other drugs for the deceased were conducted, and results are pending, officials said.

Snow was reported on the shore and a nearby weather station recorded a top wind gust of 39 mph at around the time of the accident shortly after 3 p.m. By 4 p.m., the weather began to clear, and the skies were cloudless again shortly before 5:30 p.m., the report said.