WELLINGTON (REUTERS) - The minor stroke suffered by former All Blacks scrum-half Piri Weepu this month may have been caused by a hole in his heart, the Auckland Blues said on Friday.

He was ruled out of all rugby for at least four weeks on Thursday after doctors, attempting to find the cause of his migrane-like symptoms, discovered he had suffered a minor stroke on March 1.

The 30-year-old, however, played three Super Rugby games before he had a scan on Monday.

A spokesman for the Blues told local media on Friday that further checks had discovered a small hole in his heart which is likely to have caused the stroke.

The 71-Test World Cup winner would see a cardiologist next week to determine the next course of treatment. Surgery was an option.

Weepu was released from hospital on Thursday and attended the Blues' training session on Friday ahead of their clash with fellow New Zealand side the Otago Highlanders at Eden Park on Saturday.