European competition commissioner Neelie Kroes could impose a fine of up to €500 million on German energy company Eon for allegedly tampering with a seal on a room containing confiscated documents.

Yesterday a spokesman for Eon denied deliberate interference with the seal, placed on the room during a raid on the company by EU anti-trust investigators in May 2006.

"The seal was not damaged voluntarily," said the spokesman. He suggested it had dropped off the door of its own accord because of vibrations through the wall from door-slamming in adjacent rooms. He insisted no documents had been touched or removed.

"If the commission imposes a fine, we are ready to take all legal measures to defend our position."

The commission stood by its position yesterday that the seal was tampered with immediately after a raid on an Eon office in Munich on May 29th, 2006, on suspicion of breaches of EU energy cartel practices.

Investigators confiscated documents from the entire office and collected them in one room, placing a special security seal on the door. The following morning, according to the commission, investigators found that the seal had clearly been tampered with.

"It's a special seal and, when tampered with, the word 'void' appears all over it," said a spokesman for Ms Kroes yesterday.

"The infringement has taken place because the seal was broken - we are confident of that. It is irrelevant whether the room was entered or documents were touched."