Wet lumber stains on concrete

New construction garages with wet lumber stains from storing it in the garage. Their normal cleaning contractor can't get it out. What should I try om it so I can save these guys the expense of having the garage coated and look like the hero?

What did he try on it? Are you saying that this is a stain other than where wet wood sat and probably mildewed?

Hi Roger. Unfortunately, I don't know exact prior attempts. I've seen them working before and noticed a standard Zep concrete cleaner in use, so that was probably the case here as well.

The stain itself is 8' long and yellow/orange--as if the lumber was dyed and the dye transfered while wet. May have been some pressure treat in the pile too so those chemicals may be part of it. Doesn't really have a mildew look to it (plus we are quite a dry location despite the storm that caused these issues).