EAD additional evidence?

My LG submitted his EAD application to TSC one month ago. Today he got the following notice: On December 30, 2005, we mailed a notice requesting additional evidence or information in this case …..

We submitted:
I-765 form
Copy of his I-140 approval notice
Copy of his I-485 receipt notice
Copy of passport, visa, and I-94 card
His H1b approval notice

What additional evidence they should ask?

Any information will be appreciated. Thank you.

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