(Adds shutdown details, quote and number of injured)

By Ana Isabel Martinez

MEXICO CITY, July 23 (Reuters) - Mexican state oil giant Pemex said on Wednesday that work at most of its Ciudad Madero refinery in northern Mexico had been halted while it tried to contain an ongoing blaze in a storage tank.

"Most of the refinery plants are stopped for security," said a Pemex spokesman, adding that there was a very low risk of the fire spreading to other parts of the refinery, located in Tamaulipas state.

Local television images showed out-of-control flames at the site, where the blaze began during the night in a gasoline storage tank.

Pemex said nine people had been lightly injured and around 200 people who live near the refinery had been evacuated.

The company said firefighters were waiting for the gasoline to burn off, most likely by the afternoon, before the fire could be fully extinguished.

The Ciudad Madero refinery is the smallest of Pemex's six domestic refineries, with a total crude processing capacity of 190,000 barrels per day.

(Additional reporting by Simon Gardner and Veronica Gomez; Editing by Paul Simao)