Shares in Nissan Motor Co fell sharply on Monday after the Japanese automaker said tens of thousands of vehicles had been produced without proper safety checks, raising the possibility of a wide recall.

Nissan said it has temporarily suspended registrations of around 60,000 new vehicles after Japanese government checks found that unqualified personnel had carried out final safety checks at six domestic factories, including group company plants.

Nissan’s shares fell as much as 5.3% to 1,054.5 yen in early trade on Monday, their lowest since April, before paring losses. The wider Nikkei average was flat.

At a press conference on Friday, Nissan could not say from when the inappropriate checks had been carried out, or the total number of vehicles that could be involved.

The automaker said it has temporarily suspended registrations while it re-inspects affected vehicles, adding that a third party will take part in its internal investigation.

The Ministry of Land, Infrastructure and Transport, which carried out the checks, said on Friday it has asked Nissan to report measures to prevent a recurrence by the end of October.