Large swarm of mayflies closes US bridge

It may look like a snow storm but this is actually a huge swarm of flies that have caused chaos in the US state of Pennsylvania.

Thousands of mayflies made their way onto this bridge turning the road surface into a slippery mess.

The poor road conditions caused a couple of drivers to crash but luckily no one was hurt.

Piles of mayflies over half a metre deep were seen the morning after.

The bridge was closed late on Saturday, reopening early on Sunday, police said.