BEIJING - A month away from the opening of the Shanghai World Expo, security has been beefed up nationwide in China.

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Police have launched a nationwide campaign to control dangerous substances such as explosives, firearms and ammunition, toxic chemicals, and radioactive substances, said Public Security Ministry spokesman Yan Zhengbin at a news conference Wednesday.

All manufacturers of these substances would be inspected for safety risks, and managers of related firms based in Shanghai and adjacent regions were required to file daily security reports to local police offices, Yan said.

Police in Shanghai had to prevent any dangerous materials entering the city and the Expo venues.

Searches would be carried out at railway stations, road checkpoints and airports, Yan said.

The ministry also released a notice Wednesday, requiring strict ID checks on people sending mail and express deliveries to Shanghai during the Expo.

Postal workers were required to ask for valid identity cards, and to take detailed information on senders and the mail items sent to Shanghai.

Mails sent to the Expo park should be collected at a designated post office inside the park, and unauthorized express deliveries were forbidden in the area, the notice said.

Post offices had the right to require recipients to open mail or express items if security checks needed.

Post offices should not send unknown electrical equipment, powders, unidentified gases or liquids, the notice said.