Shanghai metro experienced a spate of problems between Monday and Tuesday with a record three breakdowns within two days, causing massive delays with stations crowded and travelers sweltering in summer heat during rush hours.

The Metro Line 2 was operating at a limited speed and experienced long departure intervals at 8:15 am on Monday because of equipment failure in one train. The faulty train was towed away after eight minutes but the disruption lasted for almost half an hour.

Five extra trains were sent to the line's sections in the Pudong area to alleviate congestion, a Metro official said. Line 2 resumed operations by 8:40 am.

Yin Wei, an official with the Shanghai Metro Operation Co, said a signal failure occurred on Metro Line 1 at the southwest end at Xingzhuang Station around 8:40 am. The failure wasn't fixed until one hour later and operations were affected for long afterward.

Signal equipment failure was also responsible for disruption on Metro Line 2 on Tuesday night, said Yin. It happened around the evening peak of 6:30 pm.

Metro Lines 1 and 2 are the busiest and oldest in Shanghai.