29 CFR §102.75

If it appears to the Regional Director that issuance of a complaint may be warranted but for the pendency of a petition under Section 9(c) of the Act, which has been filed by any proper party within a reasonable time not to exceed 30 days from the commencement of picketing, the Regional Director will suspend proceedings on the charge and will proceed to investigate the petition under the expedited procedure provided below, pursuant to the first proviso to subparagraph (C) of Section 8(b)(7) of the Act.