The Impact now have seven days to make an offer to the 29-year-old Soumare, a seven year MLS veteran who played most recently for the Chicago Fire. The former MLS all-star also spent three years playing in France.
Toronto FC collected a fourth-round pick in the 2015 draft for Hall, whose contract option the club had already declined. Hall, 26, made 67 appearances in three seasons with Toronto.
New England is Hall's fifth MLS stop after the New York Red Bulls, Portland, FC Dallas and Toronto.
Toronto and Vancouver both passed in Thursday's re-entry draft, which saw eight players taken by six clubs.
The San Jose Earthquakes made two selections, taking defender Marvell Wynne second overall and midfielder Sanna Nyassi in the second round. The Houston Dynamo also selected twice, choosing forward Chandler Hoffman and midfielder Nathan Sturgis.
New England took forward Tristan Bowen, Orlando selected goalkeeper Josh Ford and FC Dallas brought midfielder-forward Atiba Harris back in the fold.
In other MLS moves Thursday, Sporting Kansas City signed Chilean international goalkeeper Luis Marin to fill the void left by the loss of Eric Kronberg (Montreal Impact) and Andy Gruenebaum (San Jose Earthquakes) in Stage 1 of the re-entry draft last week.
Marin was a member of Chile's 23-player roster for the 2010 World Cup in South Africa and has eight caps for Chile. Most recently, Marin, 31, has played for Universidad de Chile in Chile's top league.
"Luis (Marin) is a goalkeeper with a wealth of experience and leadership," Sporting Kansas City manager Peter Vermes said in a statement. "He knows our team and the tasks that lie ahead for him and he is raring to go to take the challenges head-on."
Kansas City also signed Hungarian international Krisztian Nemeth. The 25-year-old forward last played for Dutch club Roda JC Kerkrade, scoring eight goals in 25 games during the 2013-14 season.
Nemeth is the fifth addition to Kansas City's roster for the 2015 season, along with defender Jalil Anibaba, midfielder Bernardo Anor, midfielder James Marcelin and Marin. The club re-signed star forward Dom Dwyer on Wednesday.
NOTES: England's Stoke City says U.S. international Brek Shea is headed to Orlando City SC ... The Portland Timbers have named former Wake Forest coach Jay Vidovich the head coach of its new USL PRO team known as Timbers 2 ... Houston signed former D.C. United goalie Joe Willis to a new contract.
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