BEIJING -- No disease-causing viruses were found on China-exported frozen strawberries allegedly behind a food poisoning outbreak in Germany, China's quality watchdog said on Thursday.

The Noroviruses, which were suspected of sickening more than 11,000 students in east Germany as reported by foreign media last week, were not found on sample products of the Chinese company that exported the strawberries, according to a statement issued by the General Administration of Quality Supervision, Inspection and Quarantine, or AQSIQ.

All the company's inventories have been sealed for investigations and lab tests, which returned no scientific evidence to indicate the strawberries were contaminated before being exported, the AQSIQ said.

The company, based in East China's Shandong province, has exported frozen strawberries to eight other nations this year but no similar incidents were reported, the AQSIQ said without specifying the company or the eight countries.

The administration noted the German side needs further investigation to identify the source of contamination as frozen strawberries have a long supply chain that includes production, transportation, distribution and catering. It added that China would like to enhance communication and cooperation with the European Union and Germany for the investigation.

The AQSIQ also ordered intensified quality supervision on the country's exported frozen strawberries.