IT was balloons that crippled the Maglev airport express on Wednesday morning, Shanghai's electric authority said yesterday.

Shanghai Electric Power Co Ltd, the city's power supplier, said a 220-kilovolt electric line in the Pudong New Area was tripped by the threads of some balloons, which were released by a commercial plaza during the opening ceremony.

The instant voltage fluctuation affected the power system of the nearby Maglev, and the operator of the express halted the very first train at 6:45am, which had just left the Longyang Road station.

No punishment for the commercial plaza has been reported, according to the power company.

"Such cases of outer forces breaking down the power supply always happen," said Wang Changxing, media officer of the company.

"People and company don't pay enough attention to power utility protection, which is a big hidden hazard."

He appealed to locals to pay more attention to the power utilities.

Wang said the country launched a power utility protection regulation last year but was not well enforced.

"I don't think they have enough people in the law enforcement team," he added.

About 70 commuters among the 269 passengers missed flights because of the breakdown, according to the operator. It took nearly an hour for service to resume.

Also on Wednesday morning, households and companies near Dongtang Road in Pudong lost power after a car crashed into a wire pole there.

Three power breakdowns by outer forces and over 10 electricity facility theft cases were reported in the past week, Wang told reporters.

"Even on the opening day of the World Expo, there were still people found flying kites under the high voltage grid in urban areas, which could've caused the power failure on the opening ceremony."