The fires were spotted in a car parking lot and at three other locations within a 3-kilometre evacuated area, the official Xinhua News Agency said.
It did not give more details, but the state-run Legal Evening News said firefighters put out the fire in the parking lot and that cleanup work in the disaster zone soon resumed.
Technicians have detected levels of cyanide as much as 356 times the safe level within the evacuated zone, although no abnormal contamination was found outside the zone, according to state media reports.
Xinhua said excavating equipment was being used to clear the site, and trucks were carrying out debris.
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Officials have ordered nationwide checks on dangerous materials. Driving home the importance of such efforts, President Xi Jinping and other top leaders gathered in Beijing to hear a report on progress in investigating the disaster.
"Lately, in some places there have been major industrial safety accidents, one after the other, revealing yet again that problems in the area of industrial safety remain prominent and grave," said a statement issued after the meeting yesterday.
The Ruihai owners were able to secure permits to store toxic chemicals, including sodium cyanide, ammonium nitrate and potassium nitrate, even though their facility is located less than the required 1,000 metres from homes and public roads -- a clear violation of state safety rules.