A lorry crane hit the roof of a Central Expressway (CTE) tunnel yesterday afternoon, damaging light fixtures and causing the tunnel to be closed until about 6pm.
The accident occurred in Upper Cross Street on the slip road to the CTE at about 1pm, and the tunnel was closed around 1.30pm. But the crane was towed out only at 4.40pm.
The Land Transport Authority (LTA) said preliminary investigations showed that the lorry did not have its crane adequately stowed.
Police said the driver, a 63-year-old man, was arrested.
At about 4pm, traffic in the area was flowing smoothly but eyewitnesses said the accident had caused a jam earlier in the day.
"I passed by in the early afternoon and there was a jam," said a maintenance worker who wanted to be known only as Mr Ong.
An LTA spokesman said: "LTA had removed the damaged tunnel light fixtures and assessed the tunnel was safe for the public's use before it was reopened."
Full maintenance works will be carried out between midnight and 5am.
Since 2013, there have been at least 20 cases of overhead road structures being hit by vehicles over the general height limit of 4.5m. Just last week, the LTA announced that all lorry cranes must be fitted with an audio warning system from next year to reduce the risk of their crashing into overhead road structures.