Helicopter crashes on US highway, killing four

US officials say a commercial helicopter crashed onto a Maryland interstate highway and burst into flames, killing all four people on board.

The chopper was engulfed when firefighters arrived at the scene minutes after receiving a call at 10.30pm local time (02.30am Irish time).

No vehicles on the highway were hit when the helicopter smashed into the eastbound lanes of Interstate 70.

Visibility was limited slightly by fog at the time of the crash, but it was not clear whether weather played a role, officials said.

Storms had also passed through the area earlier in the night.

A witness is reported to have seen the helicopter flying low when a bright arc of electricity flashed in the air, apparently caused by the chopper striking a power line. It was not clear whether it was already on its way down when it hit the lines.

Before seeing the arc, the witness thought the helicopter might have been trying to land along the roadway.