WASHINGTON: The US State Department is closely following reports of an explosion in Beirut and stands ready to offer 'all possible assistance', a spokesperson for the agency said, as a massive blast ripped through the Lebanese capital on Tuesday, killing at least 10 people and injuring hundreds.

The Department has no information about the cause of the explosion, the spokesperson said and added that the agency is working closely with local authorities to determine if any US citizens were affected in the incident.