(Updates with details on cause of blasts, Defence Ministry comment)
SANAA, Oct 18 (Reuters) - A shell fired near a Yemeni general's military headquarters in the capital Sanaa hit a weapons depot and set off a series of explosions on Thursday, a Yemeni army source said.
A Reuters witness said he heard two blasts and saw a large cloud of dust above the camp, where General Ali Mohsen al-Ahmar is based. Ahmar defected during last year's uprising against Ali Abdullah Saleh and leads part of the army under Saleh's successor, President Abd-Rabbu Mansour Hadi.
A source in Ahmar's force, known as the First Division, said a shell fired from outside the camp had landed on an ammunition cache, setting off the explosions.
He said there were no casualties and an investigation was under way to determine who fired the shell.
The Yemeni Defence Ministry said the blasts were caused by an accident in ammunition depots.
Ahmar broke away from the Yemeni army shortly after street protests against Saleh's 33-year-rule broke out early last year, and said his move was aimed at protecting demonstrators who had set up a protest camp in the centre of the Yemeni capital.
Hadi is trying to reunify the armed forces, which are still partly controlled by relatives of the former president. (Reporting by Mohammed Ghobari; Writing by Sami Aboudi; Editing by Louise Ireland and Rania El Gamal)