The suspects were first detained Thursday when dozens of police officers launched raids in Belgium and Portugal, investigating suspected graft within the EU parliament.

The scandal comes two years after several EU lawmakers were accused of being paid to promote the interests of Qatar and Morocco -- something both countries deny.

A Belgian judge on Tuesday charged four people with "active corruption and criminal organisation" and kept them in pre-trial detention, the federal prosecutor's office said.

A fifth, charged with money laundering, was released under conditions.

The fresh searches at the offices in the EU Parliament took place on Monday, it added.

Huawei has said previously that it takes the graft allegations "seriously".

"Huawei has a zero-tolerance policy towards corruption or other wrongdoing, and we are committed to complying with all applicable laws and regulations at all times," the company said on Friday.