NEW ORLEANS (AP) — Researchers searching for a possible mass grave from a racial massacre in 1887 said they picked up signals last month of disturbed earth at a south Louisiana site, but they cautioned they don’t know yet what ground-penetrating radar detected. The signals were detected Thursday, May 17, the first day of a survey of a vacant lot in the community of Thibodaux, where locals believe white mobs dumped the bodies of African-Americans killed during a Reconstruction-era rampage. The mobs were out to break a monthlong strike by sugar plantation field hands, many of them ex-slaves, in the era following the American civil war.