Updated at 6:08 p.m. ET
TRIPOLI, Libya - Hospital officials say an explosion at an ammunition depot near Libya's rebel stronghold of Benghazi has killed at least 17 people and injured at least 10.
Dr. Habib al-Obeidi says Friday's blast hit nearby houses and he fears the toll could rise because ambulances are still bringing people to the al-Jalaa hospital.
The cause of the blast is unclear. Al-Obeidi says it apparently was triggered when people went into the storage facility to collect weapons, but others blamed pro-Qaddafi forces for triggering the blast. Witnesses say secondary explosions are continuing and several areas have been set on fire.
The blast comes on a particularly deadly day in Libya.
Leader Muammar Qaddafi's forces launched a powerful attack trying to take back the closest opposition-held city to the Libyan capital Friday, in fierce fighting that killed at least 37, including the city's top rebel commander an army colonel who defected. In Tripoli, Qaddafi loyalists fired tear gas and live ammunition to smother a new outbreak of protests. And rebels captured a key oil installation at Ras Lanouf after a day of brutal, back-and-forth fighting.
"The pro-Qaddafi forces have started beating up the protesters," CBS News' Vicki Barker reported from Tripoli's Green Square. As she was speaking, Barker was interrupted by the sound of at least five gunshots.
The fighting underlined how both sides are pushing against the something of deadlock that has gripped Libya's 18-day-old upheaval. The rebellion has broken away the entire eastern half of the country from Qaddafi's control and has swept over several cities in the west close to the capital.