Three Tesla Motors employees were killed in Palo Alto on Wednesday when their small plane struck power lines following takeoff. The National Transportation Safety Board is currently investigating the plane crash, but have not revealed any findings yet.

This is second fatal private aviation accident involving power lines this year.

In early January, a helicopter carrying three scientists and a pilot crashed into unmarked power lines in California, causing a fire on the craft that killed all four. The Federal Aviation Administration places the responsibility of placing lights and markers on power lines with the companies that own them, but does not require it.

At this time, unmarked power lines are not believed to have been a factor in Wednesday's fatal plane crash.