An Windsor-area manufacturer stands behind its girders, despite the province announcing it's expanding its review to all concrete support beams used in the $1.4-billion Herb Gray Parkway project.

The government says there are questions about whether the girders used to build some overpasses and underpasses are up to code.

The review panel is now looking at girders built by Prestressed Systems Inc. and not just the ones built by Freyssinet.

Girders built by that Spanish company sparked the review in July, when the government learned the company had allegedly used a process called tack welding to hold the steel rebar together inside the concrete girders. The method, the government says, does not meet a federal building code.

In July, a spokesperson for Prestressed Group, which manufactures concrete girders at its Walker Road facility, said it is was not their girders in question.

Since the review began last month, the government closed the South Talbot Bridge, one of the first overpasses built during the project and one that used Prestressed girders, which also contain tack welding.

"It should be made clear that tack welding under the Canadian Bridge and Highway Design Code is allowed under strict guidelines with respect to materials, welders and procedures and this process of tack welding has been used for over 20 years on other Ontario projects," Prestressed said in a statement. "Based on this, we wish to emphasize that all girders produced by PSI on this project, including the ones used in the North Talbot structure, were produced using drawings, details and procedures that were in strict compliance with those guidelines. We are therefore confident that the evaluation being conducted by the expert review panel will result in the continuing acceptance of these girders."

The panel is to complete its review by the end of the month after a 30-day extension.

Infrastructure Minister Glen Murray cautioned against jumping to conclusions.

"No one's accused of any wrongdoing here. This is an engineering exercise," he said. "I've asked people to wait until the review comes out. The expert review panel is a group of some of the most authoritative engineers on structural engineering.

I've asked for a very clear recommendation from them exactly on what the government should do to comply with the law."

If the province finds the tack-welded girders are not up to code, they may have to be removed from the project.

Of the 560 girders made by Freyssinet, about 320 girders were installed at two unopened structures - Tunnel 2, known as the Labelle Tunnel and Tunnel 7, known as the Villa Borghese Tunnel.

As CBC News was first to report, Ontario's Ministry of Transportation said it knew in "late 2012" a number of girders manufactured for the Herb Gray Parkway did not meet code. Some of those girders were installed in January.

Meanwhile, people who live near the North Talbot Road overpass are becoming impatient, since it's been closed for the past couple of weeks.

"It is really big problem for us because we cross the bridge every day," said resident John Jamil. "People go to work, come from work, buses, school buses, public buses, they all suffer."