Malaysia's nuclear energy regulator has sealed off a pharmaceutical company following a radiation leak earlier this month, a minister said Wednesday.

Science, technology and innovation minister Maximus Ongkili told AFP the Atomic Energy Licensing Board (AELB) sealed off the company after four of its employees set off radiation monitors when visiting the AELB's office on June 2.

"The radiation reading on one of the workers exceeded more than 400 times the normal reading (of 0.5 microsieverts per hour)," he said.

Ongkili said the AELB checked the company's premises in central Selangor state on the same day, finding the contamination there at 100 times the normal reading and sealed off the area to "ensure the radiation did not spread and prevent any radioactive particles from leaving the place."

He said three of the four went through a decontamination process at the National Radiological Emergency Centre, while the fourth worker with the high radiation exposure as a result of being "directly involved in the radiopharmaceutical leakage," was treated at the Malaysian Nuclear Agency.

"In this case, the radioactivity has a half life of two hours, therefore after 20 hours, the background reading at the company returned back to normal," Ongkili said.

"However, the company has been temporarily closed pending an assessment by the AELB on the firm's new radiation protection programme," he added, but declined to identify the company or the source of radiation that was leaked.

Although it does not have any nuclear power plants yet, Malaysia is home to several pharmaceutical and manufacturing companies that rely on radioactive materials to make their products.

Last December, the government said it was looking to build two 1,000 megawatt nuclear power plants by 2022 to counter an "imbalance" in its energy supplies.

The plan has been attacked by environmental activists who say the government has not thoroughly considered other forms of energy generation such as solar, hydroelectric and wind power.