Trader-Turned-Informant Tied to Waste Stock That Surged 1,500%

Three tiny stocks that went haywire in the past month have one thing in common: a former FBI informant.

Shares of Avalon Holdings Corp., New Concept Energy Inc. and MER Telemanagement Solutions Ltd. skyrocketed and then dropped around the time that MintBroker International Ltd. revealed stakes in the firms, all of which have market values of less than $30 million.

MintBroker is a Bahamas-based broker dealer founded in 2011 by Guy Gentile, according to a lawsuit filed by the trader-turned-informant earlier this month. Gentile began working as an informant in 2012 after the FBI said he orchestrated two pump-and-dump ...