Toyota Motor has extended until March 1 the shutdown of two production lines at two manufacturing plants run by a group of companies in Japan, it said on Friday.

The production lines have been suspended since Jan. 29 after the discovery of irregularities in certification tests for diesel engines developed by affiliate Toyota Industries .

On March 1 Toyota will make a decision on whether to reopen the lines from Monday March 4.

However, the suspension will continue for one line at Toyota Auto Body's Inabe plant in Mie prefecture, where production includes the Alphard and Vellfire minivans, and one line at Gifu Auto Body's main plant in Gifu prefecture, where production includes the HiAce van.

(Reporting by Maki Shiraki; writing by Anton Bridge; Editing by Michael Perry)