A judge in the Spanish territory of Ceuta which borders Morocco summoned the 16 members of the Civil Guard military police for questioning to assess whether they could be responsible for the migrants' deaths, judicial authorities said in a statement.
The migrants drowned on February 6, 2015 while trying to swim from a beach in Morocco to Ceuta, one of Spain's two north African territories.
Witnesses accused Spanish security forces of firing rubber bullets at the migrants in the water. The government admitted rubber bullets were used but denied its forces targeted the migrants directly.
The judge summoned the Civil Guards to come along with their lawyers for questioning between March 3 and 11, said the statement from the high court in the southern Andalucia region which also covers Ceuta.
"The judge will investigate whether the actions of these guards and their use of rubber bullets could have contributed to the death of the five immigrants who were found on Spanish shores," it said.
"The investigation of the events will have to determine whether the officers could be responsible for a possible crime of negligent homicide."
It added that the court had requested information from Moroccan authorities about other bodies which were retrieved on the Moroccan side and autopsy results.
A Spanish non-government group working with migrants in Morocco, Caminando Fronteras, says it identified the 15 people who died as migrants from
Cameroon, Senegal, Guinea and Ivory Coast.
The news of the summons "is very important for the victims' families," said a member of the group, Helena Maleno. "They want justice. They want to know who killed their sons and daughters and why."
Spain has been accused of breaching the human rights of migrants trying to enter Ceuta and its other African territory, Melilla, including many who climb the high fences that separate the territories from Morocco.
Thousands of migrants seeking a better life in Europe try every year to enter the two cities, which have Europe's only land borders with Africa.