SANTIAGO – Fears of tougher mining regulation in Mexico under incoming President Andres Manuel Lopez Obrador are taking over investor sentiment, with some of the top stocks falling for the third consecutive day.

Industrias Penoles SAB, Grupo Mexico SAB and Fresnillo Plc extended losses after Morgan Stanley downgraded the stocks on concerns that Mexico’s new congress is considering as many as 11 bills or resolutions that could materially impact mining companies operating in the country.

On Tuesday, an initiative from Morena party Senator Angelica Garcia called for increasing surveillance of mining activities and giving greater powers to communities and the government.

“We believe Mexican mining equities will decouple from fundamentals for the foreseeable future given the heightened uncertainty around the regulatory framework,” Carlos de Alba, an equity analyst at Morgan Stanley, said in the report. “The risk ranges widely and could be material.”

Proposed initiatives include empowering the Ministry of Economy to declare certain zones as not viable for mining, and revoke permits and existing concessions that had a negative social impact. They also contemplate charging Mexican agencies with overseeing the social and environmental impact of mining activities.

The first nine bills tabled in congress could impact Mexican miners’ Ebitda that originates from mines in the country by as much as 3% for Fresnillo, 2% for Penoles and 1% for Grupo Mexico, Morgan Stanley’s report said. Miners would also see a 5% reduction in revenue from mining operations located in indigenous territories.

Grupo Mexico was down 6.7% on Thursday at midday local time, while Penoles lost 3.8%. The two companies were leading losses in the Mexbol stock index for the second consecutive day, and had fallen to the lowest in more than two years. Fresnillo, which is listed in London, plunged 12% on Thursday, the biggest decline in five years.