More than 30 bullet trains were brought to a halt by a power failure on the Beijing-Shanghai high-speed railway on Tuesday.

That marked the second time a power loss has caused travel delays in the 12 days since the train began operating on June 30.

Railway authorities said an electrical failure occurred in the power grid system near Suzhou, a city in Anhui province, at 11 am on Tuesday.

In a short news release, the authorities said the glitch had been dealt with by 1 pm and that travel on the railway had resumed soon afterward.

The mishap occurred just two days after another power loss on the line. Thunderstorms on Sunday evening disrupted the electrical supply to the railway's Qufu-Zaozhuang section, causing 19 southbound trains to be delayed.

In response to the troubles on Tuesday, railway bureaus in Shanghai and Beijing apologized on their official micro blogs and refunded money to passengers who had canceled their trips.

Even so, the authorities stopped short of explaining the cause of the power failure.

According to accounts railway passengers posted to micro blogs, the power loss led to at least four trains being temporarily stranded in places where there was no bad weather on Tuesday.

Wu Junyong, a professor specializing in railroad electrical engineering at Beijing Jiaotong University, told China Daily: "Judging from a picture posted at Sina.com.cn, an overhead electrical line was burnt, which caused the trains to halt."

The photo, though, offered no indication of how the damage had occurred to the line. Possible causes of the malfunction include an inadequate installation of the wire or the use of poor-quality wire.

"This is an equipment malfunction, severer than the incident on Sunday, when the train cut off its own power supply to protect itself (after lightning hit the overhead lines)", he said.

The malfunction on Tuesday has generated a new round of online discussion and suspicion about the railway, which opened one year ahead of schedule.

Some netizens and experts responded by calling for tolerance and patience.

Wu said that it is common for malfunctions to occur when trains first start to run on a high-speed railway. Such railways are complicated operations and cannot be expected to run free of glitches until various adjustments have been made to it over time.

"The Beijing-Shanghai high-speed rail stretches for 1,318 km and crosses four provinces and three municipalities," he said. "That malfunctions would occur on such a long line when it has been operating for less than two weeks is inevitable and understandable.

"Such malfunctions will become less common after it has been operating for a while longer."

According to previous media reports, trains on the 1,069-km Wuhan-Guangzhou high-speed rail, which has a maximum speed of 350 km/h, were delayed at least five times in the three months after the railway began operating on Dec 26, 2009. Those delays were blamed on equipment malfunctions.

As for the power failure on Sunday, Wu said similar things occur in southern France, where gales and lightning often cause high-speed railways to malfunction. He said foreign and domestic technology cannot be expected to completely shield high-speed railways from the effects of bad weather.