It was believed to have been caused by a build up of methane.

He suffered from a heart condition which was believed to have been caused by his steroid use.

The blast was believed to have been caused by gas.

His illness was believed to have been caused by the bad weather in the inauguration.

Its extinction is believed to have been caused by human activity.

The fire is believed to have been caused by human negligence.

Nine patients died during the studies, the agency said, but none of the deaths were believed to have been caused by the device.

The fire was believed to have been caused by a camp fire.

While some fires are believed to have been caused by environmental factors, others clearly were not.

This crash is believed to have been caused by bad weather.