Shanghai:Things are heating up on Line 5, but everything's under control as metro authorities have put buckets of ice on carriages to keep passengers cool while they work out the air conditioning kinks.

Officials said yesterday that the air conditioning on the line's trains won't be functioning until the end of October.

Metro authorities said they had already refitted air conditioners on 14 trains in use on lines 6 and 8.

Work began on 66 trains for the three lines in July after commuters complained about stuffy carriages.

A different method for renovations slowed work on Line 5 trains, officials said.

But to appease hot and sweaty passengers, authorities put buckets of ice on carriages.

"It was just an expedient measure," said Yu Shichang, a director with the Metro operator.

Yu said extra manpower was needed to put the ice on the carriages, which cost thousands of yuan each day.

Line 5 trains run from Xinzhuang area to Minhang Development Zone both above and below ground, causing temperatures in carriages to fluctuate, the authorities said.

Ice has been used on carriages to keep passengers cool in the past. Metro Line 1 used ice in trains before 2006, but discontinued the practice when new trains were put into service.