Switzerland will return 4,400 Roman artifacts to Italy which were seized from a Basel art dealer and were probably stolen from illegal digs, the SDA news agency reported on Thursday.

The objects include vases, statues, mosaics and bronze items from pre-Christian times which were found in the Basel warehouse of an Italian art dealer as part of an investigation launched in 2001 on Italy's request.

"We felt like we had been transported back to ancient Rome," the SDA agency quoted investigator Mario Plachesi as saying.

After 80 officers worked for months to catalogue the items - most of which are likely from Apulia in southern Italy - the Swiss authorities are now handing them back. A further 1,400 artifacts, probably from Greece, were also found in the warehouse but will stay in Basel.