Flames and thick clouds of black smoke rose from the site near the town of Qab Elias, around a hour's drive east of Beirut, and at least one explosion was seen in footage broadcast by Lebanon's MTV.
A security source said the cause of the fire was not immediately known.
Lebanon is hosting at least 1 million registered Syrian refugees, many of them living in informal tented settlements scattered around the country. The government says there are some 1.5 million Syrians in the country.
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